The invention relates to a multi-gear cassette with different sized sprockets for engaging a chain and for transferring a longitudinal force from the chain to a hub of a rear wheel of a bicycle with the possibility of transferring the chain from one sprocket to another by using a shifting device, whereby a ring-shaped element is arranged in a transition area between one sprocket and a next larger sprocket.
With multi-gear cassettes of the usual type, a cassette consisting of a number of sprockets with different diameters is mounted on a driver of a hub. When a shifting device is actuated, teeth of each sprocket come into engagement alternately with the chain and transfer torque from the rider's pedal forces to the driver by way of a profile that connects the sprockets to the driver so they rotate together. Thus, each of these sprockets individually transfers the torque to the driver, whereby both the carrier profile as well as the sprocket must be designed so they are sufficiently strong to resist lateral forces from the chain and thus heavy.
To fulfill different requirements, for example for ever-lighter construction in bicycle racing, or as a result of increased demands for precision in connection with a further increase in the number of gears, the solution of a single-unit construction of multiple sprocket devices has been implemented.
Thus, a multi-sprocket device has become known from US 2008/0230344, in which several sprockets are formed on a conical support structure, in which cylindrical and disk portions alternate in a step shape and in which each single sprocket portion is formed by a disk portion and has teeth arranged on its periphery for engagement with a chain. The support structure can be designed with very small wall thickness, which is limited toward the minimum mainly by the manufacturing tolerances. The stability is greater due to the alternate cylindrical and disk portions in succession than with a continuously conical support structure with the same small wall thickness.
In DE 10 2008 010 904, a solution is selected in which openings are worked into the step-shaped and overall conical support structure at the places where only low loads are to be transferred, starting from an engagement force on a tooth to adjacent portions of the support structure. A webbed structure with webs results, starting from a tooth of a smaller sprocket to the adjacent sprocket portion, which in turn consists of a disk portion and the teeth. The largest sprocket in the form of an end sprocket that passes on the torque for transmission to the hub sleeve and the conical sprocket hollow element are installed to form a unit, which is supported directly or indirectly with respect to the hub axle so it can rotate.